The present invention relates to a differential protection device for a disconnecting apparatus.
The disconnecting apparatus comprises at least two electrical conductors, at least one fixed contact suitable for being connected to a corresponding electrical conductor, and at least one movable contact, the or each movable contact being movable between a closed position wherein it is electrically connected to the corresponding fixed contact, and an open position, wherein it is electrically isolated from the corresponding fixed contact. The disconnecting apparatus also comprises a measuring toroid for measuring the differential current surrounding the electrical conductors, and an actuator for activating the opening of the movable contact or contacts when a differential fault is detected via the measuring toroid. The differential protection device comprises a control member for controlling the actuator.
The invention also relates to the electric disconnecting apparatus having such a differential protection device connected to the measuring toroid and to the actuator.
From the document FR 2 850 495 A1 a differential protection device and a disconnecting apparatus of the aforementioned type are already known. The differential protection device comprises an integrated circuit connected to the measuring toroid for measurement of the differential current. The integrated circuit includes the means for comparing a signal representative of the differential current to a reference threshold and the processing means for controlling an actuator for activating the opening of the movable contacts when a differential fault is detected. The integrated circuit also comprises the signal rectification means that receive said signal representative of the differential current and the filtering means connected to the rectifier means for filtering a rectified signal provided by the rectifier means and for providing a filtered rectified signal to the comparison means.
The actuator included in the disconnecting apparatus is a relay, comprising an electromagnetic coil. The relay is connected via power supply terminals to the electrical conductors for its power supply, the power supply terminals being arranged between the measuring toroid and the movable contact or contacts.
The electric disconnecting apparatus is designed to be connected in a specific direction, that is, with the electrical source connected upstream of the movable contacts and the electrical load connected downstream from the measuring toroid for measuring the differential current. In other words, when the disconnecting apparatus is connected in accordance with the direction planned, the power supply terminals, and in particular the coil of the actuator, are arranged between the movable contacts and the electrical load.
However, when the electric disconnecting apparatus is connected in the reverse direction, that is to say with the electrical source connected upstream of the power supply terminals, and in particular of the coil of the actuator, with the electrical load being connected downstream from the movable contacts, the occurrence of an electrical fault is thus adapted for causing the destruction of the actuator.